Good morning. Welcome to "this week." A monumental man. He no longer belongs to us. He belongs to the ages. Nelson mandela. Revolutionary, president, prisoner. And prophet. Sometimes, it falls bonn a generation to be great. Let your greatness blossom. This morning, how he transformed our world. The lessons for our politics today. And a look back at his remarkable interview with ted koppel, just days after leaving prison. To spend 27 years, at the prime of your life, is a trage tragedy. Then -- we can't survive -- from wendy's to the white house. America debates inequality, growth, and fairness. We tackle it with two key senators, plus james carville and mary matalin join our powerhouse round table. Right here, this sunday morning. From abc news, "this week" with george stephanopoulos starts right now. Hello, again. In south africa today, preparations for the most massive memorial service in memory. Pope francis, four american presidents, the dalai lama and dozens of world leaders will be there tuesday to pay tribute to a giant of our time. We'll reflect on nelson mandela this morning. First, let's go to chief foreign correspondent terry moran. Just outside mandela's former home in soweto. Good morning, terry. I see the rain has started all around you. Reporter: That's right, george. Right now, the rain is just opened up on this scene here. But it hasn't dampened the spirits here in soweto, just up the street, as you say, from nelson mandela's home. You might call it the humble mt. Vernon of south africa. A remarkable, national celebration right across south africa. The passing of great man. Being marked in song, and pride, and smiles, not tears or sorrow. Today, national day of prayer and reconciliation. We were at the church in soweto, a center of resistance and sanctuary during apartheid. There and if houses of worship across south africa, prayers lifted up for nelson mandela in english, in afrikaan. In zulu in all the many tongues of this truly rainbow nation. And he was really the one that kept them together and gave them the opportunity to begin again with his courage and compassion and his remarkable capacity for forgiveness. The family issued a statement on their behalf. They're in mourning, of course. They said we have lost a great man. A son of the soil whose greatness in our family was in the simplicity of his nature. Terry, walk us through what will happen the rest of the week there in south africa. Reporter: Well, tuesday is the big day, george. That is when president obama and the other presidents and potentates and princes will come here to south africa. Join 90,000 south africans here in the fnb stadium. That is the last place the public saw nelson mandela at the 2010 world cup. He was there. He'll be there in spirit as the country says its farewell to him. There will be three days for his body to lie in state so people can come pay a personal tribute to him. On sunday, he'll be flown about 700 miles home to qunu where he'll be laid to rest in his ancestral village. Let's take a closer look at his history with the united states. He had a deep impact on our politics before setting foot on our soil. Here's jonathan karl with more. On how mandela prodded, consoles, scolded, and inspired american presidents. Reporter: Nelson mandela loomed large in america long before he was freed from prison. &#9834; It was 25 years &#9834; &#9834; that take that man away &#9834; Reporter: Inspiring a mass movement against racism and intolerance. Apartheid, no. Freedom, yes. Reporter: His relationship with u.S. Presidents has been far more complicated. When he was locked up in 1962, the u.S. Government was silent. In 1966, bobby kennedy went to south africa and took a stand against racism. Giving the greatest speech he ever delivered. Each time a man stands up for an ideal, he sends forth a tiny ripple of hope. Reporter: From lbj to nixon to jimmy carter, south africa's apartheid government was actually a u.S. Ally in the cold war. As the anti-apartheid movement grew, a young college student named barack obama was inspired by mandela to give his first political speech. The man in the white house then said no to sanctions. Against south africa, insisting they wouldn't work. Congress defied ronald reagan and imposed them any way. Reagan took his own stand against apartheid by appointing the first black man as ambassador to africa. Four years later, mandela was free. His first visit to america. Warmly welcomed at the white house. Mr. Mandela, a man who embodies the hopes of millions. Reporter: It was bill clinton with whom he would develop the closest bond. Mandela, now president of south africa, visited the white house during the darkest days of the clinton presidency. He gave his friend a boost. Our morality does not allow us to desert our friends. Reporter: This friendship clinton treasures to this day. We just hit it off. I just adored him. He was always, you know, he was a true friend. Reporter: Mandela, an ex-president, met with george w. Bush in 2005. But there was no love lost there. Mandela was one of bush's harshest critics when it came to iraq. When we talked to bush about the ailing mandela earlier this year, there were no hard feelings. He promoted freedom. He was a really great leader. He was smart and capable. And made his mark. Reporter: Obama only met mandela once. Ever so briefly as a junior senator. But his connection may be the most profound. It was mandela, he says, who awakened him to the wider world. Inspiring him to political activism. He gave me a sense of what human beings can do when guided by their hopes, not by their fears. Reporter: In other words, there night not be a president obama if not for nelson mandela. For "this week." Jonathan karl, abc news, washington.

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